1. Field of the Invention
This invention relates to a method for recovering oil from a subterranean, viscous asphaltic oil-containing formation utilizing injection of a solution containing an aromatic hydrocarbon and an acid into the formation combined with a thermal recovery method such as steam flooding or in-situ combustion.
2. Background of the Invention
In the recovery of oil from oil-containing formations, it usually is possible to recover only minor portions of the original oil in place by the so-called primary recovery methods which utilize only the natural forces present in the formation. Thus, a variety of supplemental recovery techniques have been employed in order to increase the recovery of oil from subterranean formations. These techniques include thermal recovery methods, waterflooding and miscible flooding.
The thermal recovery methods generally include steam injection, hot water injection and in-situ combustion. In addition, variations and improvements in these basic techniques have been employed such as the "huff and puff" method utilizing steam, and the reverse in-situ combustion technique. Improvements have also been set forth in the in-situ combustion method that employ the use of water injection, either simultaneously or intermittently with the air or oxygen-containing gas to scavenge the residual heat in the formation and also to improve the conformance and sweep efficiency.
My invention proposes a method which greatly enhances the recovery of oil from a subterranean, viscous asphaltic oil-containing formation by injecting a solution comprising a mixture of an aromatic hydrocarbon and an acid into the formation that synergistically reduces the viscosity of the oil combined with a thermal recovery technique such as steam flooding or in-situ combustion.